A giant Canadian pension fund has swooped to buy a big stake in Lowell Group, one of Britain's biggest consumer debt collection agencies.

Sky News understands that Teachers Private Capital (TPC), an investment arm of one of Ontario's municipal retirement schemes, signed a deal on Friday to acquire just over 35% of Lowell's shares.

The deal values the debt collection group at around $1.6bn, and returns a large chunk of cash to TDR Capital, the private equity firm which has owned Lowell since 2011.

An announcement is expected on Monday as a consequence of Lowell's publicly-traded debt securities.

Lowell specialises in debt recovery and other credit management services, a sector which has attracted frequent attention from private equity funds.

The company, which pledges to take "a fair, sensitive and ethical approach to debt recovery", competes with rivals such as Cabot Credit Management and Arrow Global, which floated on the stock exchange last October.

TPC, which is also a significant investor in TDR's funds, is understood to have been attracted to Lowell's growth prospects and its compliance record with UK financial regulators.

The deal adds Lowell to a portfolio of UK investments made by Ontario's vast teachers' pension fund, which include Camelot, the National Lottery operator; Burton's Biscuits, the owner of Jammie Dodgers and Wagon Wheels; and Busy Bees, the nurseries group.

TPC's investment comes ahead of a potential stock market flotation of Lowell, which could take place as soon as next year.